Control device for gas turbines having fluid injection augmentation systems



Nov. 16, 1954 J 5, ALFQRD 2,694,289

CONTROL DEVICE FOR GAS TURBINEES HAVING FLUID INJECTION AUGMENTATION="SYSTEMS Filed Oct. 14. 1949 Fig. 4.

r. Inventor:

Joseph S. Alfcr'd,

His At tor'n'ey.

United States PatentO Joseph S. Alford, Nahant, Mass., assignor to General Electric Company, a corporation of New York Application October 14, 1949, Serial No. 121,326 Claims. (Cl. fill-35.6)

This invention relates to gas turbine powerplants having a fluid injection system for augmenting the output of such power plants, and more particularly to an automatic control device for regulating flow through the turbine in such a powerplant.

Particularly in military aircraft service, powerplants this type are entirely adequate for propelling the aircraft at normal flight speeds but may furnish inadequate power for take-off purposes. Furthermore, special military missions often require extra bursts of speed or power for relatively short periods of time. Accordingly, it is desirable to provide means for augmenting the output of such powerplants for relatively short periods to avoid the additional weight involved if extra powerplants were provided.

One known method of providing such augmentation is by burning supplementary fuel in the exhaust system of the powerplant as described in the copending application of Edward Woll, S. N. 80,696, filed March 10, 1949, and assigned to the assignee of the present application. Other known methods of providing augmentation include injecting water or a mixture of water and other suitable fluid at the inlet of the compressor or into the combustor system, are described in a copending application of J. S. Alford, Neil Burgess, and I. G. Cruckshank, S. N. 121,328, filed Oct. 14, 1949, now Patent No. 2,551,229, and also assigned to the assignee of the present application. When certain fluids are injected at the compressor inlet, the cooling action of the fluid causes the compression process to approach isothermalcompression rather than adiabatic. As a result of this more efficient compression process, a smaller percentage of the energy available at the turbine inlet is required to drive the compressor with a consequent increase in the energy available for propulsion purposes. When the injection fluid is injected into the combustor the flow through the turbine is increased by the addition of the injection fluid. In order to pass the additional flow through the turbine nozzle an increased compressor discharge pressure is required, but the available energy at the turbine inlet resulting from this increased pressure increases more rapidly than the additional energy required by the compressor and therefore additional output is obtained as a result of the increased flow through the turbine as well as the increased available energy at the inlet.

In addition, when a powerplant of the type described is operated with fixed flow areas, a reduction in the operating temperature level of the turbine is experienced when water or a similar fluid is injected. Since the output of such powerplants generally increases with increasing temperature level, it is desirable to operate the powerplant at the highest temperature level which is commensurate with safety and desired life expectancy. Therefore any reduction in turbine operating temperature represents a loss in available output.

Accordingly, it is an object of the invention to provide a mechanically simple, compact, and efiective fluid injection control device which obviates the above-mentioned difliculties.

Another object is to provide flow control means for a fluid injection system which is safe and reliable and which automatically provides the proper turbine flow area when the fluid injection system is in operation.

Still another object is in the provision of a two-position flow control device and automatic positioning means therefor.

A further object is in the provision of means which shown) will permit operation of a powerplant with fluid injection at the highest temperature level which is consistent with safe operation during operation of the injection systern.

Other objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which Fig. 1 represents a gas turbine powerplant provided with a fluid injection augmentation system and a flow control arrangement in accordance with the invention; Fig. 2 is a detail view, partly in section, of the flow control and the operating means therefor; and Figs. 3 and 4 are views illustrating diffelr ent geometrical shapes which the nozzle flap may ta e.

Referring now to Fig. 1, a gas turbine powerplant is indicated generally at 1, having a compressor section 2, a combustor section 3, a turbine section 4, and an exhaust section 5 arranged in series flow relation to keep the powerplant weight and diameter to a minimum. The mechanical details of such powerplants are not material to an understanding of the present invention and are described with greater particularity in United States Patent 2,432,359, Streid, and in copending applications of Alan Howard, Serial Number 506,930, filed October 20, 1943, now Patent No. 2,479,573, and Serial Number 541,565, and filed June 22, 1944, and assigned to the assignee of the present application. Air is drawn from the atmosphere through an inlet 6 into the compressor section which compresses the air and thereby increases its pressure and temperature. Upon leaving the compressor section the air flows to the combustor or combustors 3 where fuel is introduced and burned with the air to increase its temperature level still further. This air under pressure and at elevated temperature leaves the combustors and flows through the turbine section 4 to the exhaust section 5 from which it is discharged to the atmosphere. The turbine extracts at least sufficient energy from the high-temperature air under pressure to drive the compressor and various powerplant accessories, and the remaining energy is available for propulsion of the aircra t.

Injector nozzles (not shown) are provided for introducing the injection fluid to the combustor section 3 of the powerplant. It is desirable, although not absolutely essential, to provide a plurality of nozzles connected to a common manifold (not shown) in order to distribute the injection fluid evenly in the combustor flow path. As previously indicated, the injection fluid may be water or a mixture of water and alcohol or other suitable fluid. The fluid is stored in a suitable reservoir 7 from which it is conveyed to the combustors 3 by conduits 8, 9. A pump 10 is provided in series flow relation with conduit 8 for eifecting flow of the injection fluid from reservoir 7 to the injector nozzles in the combustor section 3 at a suitable pressure. As already indicated, the air in the combustor section of the powerplant is under pressure since it has been compressed in the compressor section 2. Therefore, the injection pressure of the injection fluid must exceed the normal operating pressure which exists within the combustor section 3. During 'periods when the fluid injection system is not in operation the operating pressure in the combustor section 3 will tend to cause a backward flow of heated air through pump 10, and, as indicated in the above-mentioned Alford, Burgess, Cruckshank patent, a check valve (not may be provided in conduit 9 to prevent the backward flow of air from the combustor 3 through pump 10 when the air pressure in the combustor section 3 exceeds the pump pressure. Suitable means are provided for driving pump 10. The driving means may be an air turbme, as suggested in the above-mentioned copending Alford, Burgess, Cruckshank application (now Patent No. 2,551,229).

. As previously indicated, when water or other similar fluid is injected into a powerplant of the type described, a decrease in the operating temperature level of the powerplant takes place. Since this temperature reduction represents a loss in available output of the powerplant, it is desirable to provide means for increasing the operating temperature level during periods when fluid is injected so that the powerplant will operate at the highest temperature level which is consistent with safety and desired life expectancy of critical structural elements. This is accomplished in accordance with the invention by providing a variable nozzle or orifice 11 connected to the exhaust section of the powerplant.

Referring now to Figs. 2-4, the variable nozzle comprises a tab or flap portion 12 secured to a lever member 13. As illustrated in the drawing, the exhaust section 5 of the powerplant includes a wall 14 defining an exhaust passageway 15. Wall 14 terminates at an end portion which forms an opening 16 through which the exhaust gases are discharged from passageway to the atmosphere. Flap 12 and lever 13 are pivotally supported by a support member 17 secured to wall 14. Nozzle 11 is shown in the closed or small area position in Fig. 2. That is, lever 13 and flap 12 project radially inward beyond the inner surface of wall 14 to partially block opening 16. If lever 13 is caused to pivot in a clockwise direction relative to support 17 and wall 14, it will be appreciated that flap 12 will eventually reach a position where it no longer blocks opening 16.

Another support 18 is secured to wall 14 and pivotally supports a fluid motor 19 for effecting rotational movements of lever 13. The fluid motor comprises casing walls 20 defining a cylinder 21 which slidably supports a piston 22. An opening 23 is provided in wall 20 for establishing communication between one end of cylinder 21 and conduit 3. A rod 24 is secured at one end to piston 22 and at the other end to lever 13, as indicated in the drawing. Compression spring 25 biases piston 22 toward the lefthand end ofcylinder 21 and thus biases nozzle 11 to its open or large-area position.

As indicated in Figs. 3 and 4, the nozzle flaps 12 may be formed from a plate or sheet of suitable material such as stainless steel and may take the form of a minor circular segment (the smaller part of a circle included between an arc and its chord) 120, or, alternatively, an annular portion 12b. It is desirable to establish the proportions of nozzle flap 12 in such a way that the radial height r is relatively small as compared to the radial dimension of opening 16 in order to obtain good nozzle efliciency. In other respects the dimensions of flap 12 are not critical and are determined solely from a consideration of the percentage of the flow area of opening 16 which is to be blocked when nozzle 11 is in the closed position in order to match the rate at which fluid is injected into the combustor section 3 of the powerplant. In instances where it is desired to maintain a uniform pressure distribution at the periphery of the nozzle in its closed position, the flap shape 12b has been found particularly useful. In such cases a plurality of flaps 12b are provided so that the nozzle forms a substantially continuous annular wall having a central opening of smaller diameter than that of opening 16 and concentric therewith, when the nozzle is in the closed position.

During the periods when the powerplant is operating without fluid injection, there is no pressure in conduit 8 and consequently piston 22 is caused to move'to the left under the action of biasing spring 25. As already indicated, such a motion of piston '22 causes lever'13 to pivot in a clockwise direction thus moving nozzle 11 to its open or large-area position. During periods when the output of the powerplant is augmented by the use of fluid injection means, the pump 10 is in operation and is furnishing injection fluid under pressure to conduits 8, 9. As the pressure in conduit 8 approaches its normal operating value, the pressure force acting on the lefthand face of piston 22 tends to force it to move to the right, in Fig. 2, against the resisting force of biasing spring 25. The area of piston 22 and the characteristics of spring 25 are selected so that when the injection fluid pressure in conduit 8 reaches the design value, this pressure force is suflicient to cause piston 22 to move to the right against the action of spring 25 to such' a degree that nozzle 11 is moved to the closed or small-area position indicated in Fig. 2.

Thus it will be seen that the invention provides a two-position flow regulating device for use in a fluid injection system, which device is mechanically simple, safe and reliable, and is automatically operable to provide the proper flow area at all times during operation of the powerplant irrespective of whether or not the fluid injection system is in operation.

While particular embodiments of the invention have been illustrated and described, it will be obvious that various changes and modifications may be made without departing from the invention, and it is intended to cover in the appended claims all such changes and modifications that come within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination with a turbojet power plant, fluid injection thrust augmentation means, means for pressurizing. the fluid connected thereto, a variable flow area nozzle structure in the exhaust of said power plant, means for connecting the pressure means to said variable flow area nozzle structure and means to decrease the variable area with an increase of pressure.

2. In combination witha gas turbine power plant, a fluid injection power augmentation system, a variable flow area nozzle structure in the exhaust of said power plant, means to decrease the variable flow area with an increase of pressure, said nozzle structure including adjustable flow regulating means connected in series flow relation with said power plant, a source of pressurized fluid, conduit means connecting said source to said system and to said variable flow area nozzle structure, and bias means for biasing said regulating means.

3. In combination with a gas turbine power plant a fluid injection augmentation system, a source of pressurized fluid connected thereto, a nozzle defining a flow passage and an orifice for the exhaust flow from said power plant, means to decrease the size of said orifice in response to increased pressure variations in said system including a vane member pivotly supported by said nozzle about an axis transverse to the longitudinal axis of said flow passage at a location adjacent said orifice, a fluid motor operable by said pressurized fluid joined to said member, and conduit means connecting said motor to said source.

4. In combination with a 1 gas turbine power plant, fluid injection system for augmenting the. power output thereof, means for pressurizing the fluid, a nozzle comprising a flow passage with a variable discharge opening of substantially circular cross section for the exhaust from said power plant, and means connected to said nozzle and said system for decreasing the discharge opening in response to an increase in pressure of the fluid in said injection system, said nozzle including a support memberpivoted about an axis transverse to the axis of said flow passage at a location adjacent said opening and a substantially flat wall portionsecured to said support member and forming a minor circular segment for restricting said opening.

5. In combination with a gas turbine power plant, a fluid injection power augmentation system, means for pressurizing the fluid, a nozzle comprising a flow passage with a variable discharge opening of substantially circular cross section for the exhaust from said power plant, and means connected to said nozzle and said system for decreasing the discharge opening as the pressure of the fluid in said system increases, said nozzle comprising a support member pivoted about an axis transverse to the longitudinal axis of said flow passage at a location adjacent said opening, and a substantially flat'wall portion secured to said support member and forming an annular segment portion having a substantially constant radial height.

References Cited in the tile of this patent UNITED STATES PATENTS Number Name Date 2,342,262 Franz et al. Feb. 22, 1944 2,382,016 Love Aug. 14, 1945 2,395,809 Goddard Mar. 5, 1946 2,565,854 Johnstone et al. Aug. 28, 1951 2,569,497 Schiesel Oct. 2, 1951 FOREIGN PATENTS Number Country Date 919,004 France Nov. 18, 1946 

